Abstract

The first proof-of-concept demonstrations are presented for a broadband photonic-assisted analog-to-digital converter (ADC) based on spatial spectral holography (SSH). The SSH-ADC acts as a frequency-domain stretch processor converting high bandwidth input signals to low bandwidth output signals, allowing the system to take advantage of high performance, low bandwidth electronic ADCs. Demonstrations with 50 MHz effective bandwidth are shown to highlight basic performance with ~5 effective bits of vertical resolution. Signal capture with 1600 MHz effective bandwidth is also shown. Because some SSH materials span over 100 GHz and have large time apertures (~10 µs), this technique holds promise as a candidate for the next generation of ADCs.

Figures (4)

The SSH-ADC conceptual diagram. Waveform Capture: the SOI and reference waveform are converted into the optical domain and illuminate the SSH material to produce a spectral hologram. Readout: a chirped optical waveform reads the absorption profile, which is detected and digitized with high fidelity, low speed ADCs, and post processed to yield the digitized version of the SOI.

(Left) Post processing results showing the demodulated, time-domain representation of the SOI for lengths of 1,2,4,8,16,32, and 64 bits. The SOI was a 50 MSPS BPSK modulated signal on a 100 MHz and mixed onto a 6.5 GHz microwave carrier. The reference signal was a 512 bit complementary code at 400 MSPS. (Right) A zoom of the first 10 bits and shows good agreement with a simple simulation.

(a) The post-processed results as the AWG voltages are reduced showing a corresponding reduction in amplitude in the captured SOI. (b) A plot of the measured standard deviation (STD) of the waveform versus the amplitude from the AWG shown as the dots. The blue line is a plot of the expected amplitude response calculated for the EOPM. (c) The captured SOI results (black line) and simulated SOI results (blue dashed line) for a 1600 MSPS, 2048 bit binary coded SOI showing the total SOI duration. (d) A zoom of (c) showing that single bits can still be detected.